[Print Preview]: Added code to support pdf fit to page functionality.

chrome/browser/printing/print_preview_message_handler.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_PRINTING_PRINT_PREVIEW_MESSAGE_HANDLER_H_
 #define CHROME_BROWSER_PRINTING_PRINT_PREVIEW_MESSAGE_HANDLER_H_
 #pragma once
 
 #include "base/compiler_specific.h"
 #include "content/public/browser/web_contents_observer.h"
@@ skipping 42 matching lines @@
       const gfx::Rect& printable_area_in_points,
       bool has_custom_page_size_style);
   void OnDidGetPreviewPageCount(
       const PrintHostMsg_DidGetPreviewPageCount_Params& params);
   void OnDidPreviewPage(const PrintHostMsg_DidPreviewPage_Params& params);
   void OnMetafileReadyForPrinting(
       const PrintHostMsg_DidPreviewDocument_Params& params);
   void OnPrintPreviewFailed(int document_cookie);
   void OnPrintPreviewCancelled(int document_cookie);
   void OnInvalidPrinterSettings(int document_cookie);
+  void OnPrintPreviewScalingDisabled();
 
   DISALLOW_COPY_AND_ASSIGN(PrintPreviewMessageHandler);
 };
 
 }  // namespace printing
 
 #endif  // CHROME_BROWSER_PRINTING_PRINT_PREVIEW_MESSAGE_HANDLER_H_